[9] RFR (S): 8060147: SIGSEGV in Metadata::mark_on_stack() while marking metadata in ciEnv

[Roland Westrelin]

> Or does a compilation reference MethodData objects for other methods, for example when inlining? In that case you need to be sure that we create a ciInstanceKlass for the method holder of the inlined method.

We create a ciMethod for every method we inline and every ciMethod has a ciInstanceKlass reference to its holder. So we should be good.

Problem is, ciMethod::ciMethod() is:

…

  if (env->jvmti_can_hotswap_or_post_breakpoint() && can_be_compiled()) {
    // 6328518 check hotswap conditions under the right lock.                                                                                                                                                                                                                   
    MutexLocker locker(Compile_lock);
    if (Dependencies::check_evol_method(h_m()) != NULL) {
      _is_c1_compilable = false;
      _is_c2_compilable = false;
    }
  } else {
    CHECK_UNHANDLED_OOPS_ONLY(Thread::current()->clear_unhandled_oops());
  }

…

_holder = env->get_instance_klass(h_m()->method_holder());

So if jvmti is enabled, we could safepoint before we set the holder field and the method could be unloaded?

Roland.